Withdrawl (Weaning) of Mechanical Ventilation

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Introduction

In many patients mechanical ventilation can be discontinued quickly and easily. In more complex cases however considerable difficulty may be encountered.

Planning for overall ventilatory requirements should start as soon as the patient is intubated, taking into account the underlying disease process, the anticipated duration of ventilatory support required and whether a tracheostomy is required. The plan will be able to become more defined with time and the observed response of the patient.

In keeping with our philosophy of matching the degree of ventilatory support to patient need at all times, the level of support should be titrated to the minimum necessary for adequate respiratory function.

In general, ventilatory parameters should not be reduced overnight unless there is an agreed plan to do so.

All changes made to ventilator settings must be documented and clearly communicated to bedside staff.

Reduction of Ventilatory Rate

Consideration should be given to reducing the controlled rate to the lowest that can be safely tolerated from as early in the course of ventilatory management as is possible. Spontaneous breaths are supported by pressure support at the lowest level consistent with adequate tidal volume and observed work of breathing usually as evidenced by the spontaneous respiratory rate.

Assisted Spontaneous Breathing (ASB)

Many patients will be able to have their controlled rate reduced to zero before they are otherwise able to be extubated. This is desirable and in general should be considered if the following parameters are achieved:

All spontaneous breaths should be assisted by at least 5cm H2O pressure support.

Reduction of Inspired Oxygen Level and PEEP

The inspired oxygen level should be progressively titrated to maintain saturations in the range of 90 – 95%.

In general the established level of PEEP is not reduced until such time as the inspired oxygen has been reduced to 50%. The level of PEEP is then reduced in aliquots of 2.5 to 5cm H2O in conjunction with the inspired oxygen level providing that the saturations remain in the range of 90 to 95%. The following table provides a general guide to levels of PEEP associated with varying inspired oxygen concentrations.

PEEP and F1O2 Guide

FiO2

0.3

0.4

0.4

0.5

0.5

0.6

0.7

0.7

0.8

0.9

Alert the duty ICU Specialist whenever more than 60% oxygen is required. ​